Online reconfiguration in replicated databases based on group communication

Over the last years, many replica control protocols have been developed that take advantage of the ordering and reliability semantics of group communication primitives to simplify database system design and to improve performance. Although current solutions are able to mask site failures effectively, many of them are unable to cope with recovery of failed sites, merging of partitions, or joining of new sites. This paper addresses this important issue. It proposes efficient solutions for online system reconfiguration providing new sites with a current state of the database without interrupting transaction processing in the rest of the system. Furthermore, the paper analyzes the impact of cascading reconfigurations, and argues that they call be handled in an elegant way by extended forms of group communication.